An issue was discovered in OpenStack Nova before 23.2.2, 24.x before 24.1.2, and 25.x before 25.0.2. By creating a neutron port with the direct vnic_type, creating an instance bound to that port, and then changing the vnic_type of the bound port to macvtap, an authenticated user may cause the compute service to fail to restart, resulting in a possible denial of service. Only Nova deployments configured with SR-IOV are affected.